1. Field of the Invention
The present invention generally relates to a dozing system well suited for use in bulldozers; and more particularly, to a technique for automating the work cycle of digging, carrying and dumping according to data input by operator teaching.
2. Description of the Relevant Art
Normally, the dozing operation of a bulldozer is manually controlled by the operator. The operator manipulates the blade of a bulldozer by lifting, lowering, tilting and pitching in order to constantly maintain the forces exerted on the blade during digging and carrying of earth, while trying to avoid the running slippage (shoe slippage) of the vehicle body.
Such manually controlled dozing operation requires operator's skill. Moreover, the operator will get tremendous fatigue after frequent operation of the blade, no matter how skillful he is. Up to now, many attempts have been made to solve this problem and some automatic dozing techniques have been, in fact, put to practical use. One of such automatic dozing techniques is disclosed in Japanese Patent Examined Publication No. 55-36776 (1980), in which the lift amount of the blade is controlled according to the forces exerted on the blade. Another example, which is disclosed in Japanese Patent Unexamined Publication No. 7-48855 (1995), proposes automatic dozing which is performed by controlling the position of the cutting edge of the blade relative to the ground.
The conventional automatic dozing techniques including the above are not designed to take into account factors (such as, working conditions and soil properties in the field); and therefore, often encounter difficulties in meeting particular field conditions.
The objects of the present invention are to overcome the above discussed problems of the conventional art and to provide a dozing system for bulldozers which is capable of performing appropriate automatic dozing operation according to working conditions and soil properties in the field.